The present invention relates to multi-stage switching. More specifically, the invention relates to multi-stage grooming switches for use in networks.
“Switching” refers to the process of transmitting data from a set of input ports to a set of output ports. With multi-stage switching, the switching fabric includes multiple stages or nodes between the input ports and the output ports. Each node can be implemented in a variety of ways including a full N2 cross-connect or a 2N Clos network.
A Clos network or matrix is a multi-stage interconnect where each switch in each stage is connected to each switch in the successive stage by exactly one link. For example, an asymmetric 2N Clos network has N inputs and outputs and 2N center states. In general, “blocking” occurs when a connection requirement is not fulfilled. With Clos networks, there are two types of blocking: rearrangable non-blocking and non-rearrangeable non-blocking. Rearrangable non-blocking refers to blocking where the existing connections can be moved to different center stages such that a center stage switch becomes available to make the desired connection. Non-rearrangable blocking refers to blocking where a connection that is blocked cannot be created with the current set of existing connections. A 2N Clos network has been proven to be rearrangably non-blocking for bi-cast (i.e., meaning that a signal can be output on two different links or outputs). When a signal is tri-cast, there is a possibility that the Clos network will be non-rearrangably blocked. The probability of this happening can be called the non-rearrangable blocking probability.
As communication networks continue to grow, there is an increasing need to design multi-stage switches that can handle significant increases in bandwidth and efficient to manufacture and operate. Additionally, it would be beneficial to provide a method of making connections through the switching fabric and reduces or eliminates the probability of blocking.